他の人がそういうものを作っているのを見かけたので、自分もやってみようと思いました。

Prompts on PixAI are public by default, but creators can hide them on any artwork they publish. The creator of this one chose to, so the words used to generate the image stay private — only they can see them. Hiding a prompt doesn't change anything else: the artwork is still public, and you can like, comment on and share it as usual.